Track-type landing gear



March 13, 1951 e. T. DRAKELEY ET AL TRACK-TYPE LANDING GEAR 3Sheets-Sheet 1 Filed July 11, 1949 INVENTORS. 'eorye 7. DIGA E/Ey DonaldW F'lnjay REYNOLDS & BEACH ORNEYS M A m March 13, 1951 G. T. DRAKELEY ETAL 2,544,985

TRACK-TYPE LANDING GEAR Filed July 11, 1949 I5 Sheets-Sheet 2 IN V ENTORS Fay- 2. Donald W.F'1nla REYNOLDS & BEAiH EYS BYM A? March 13, 1951e. 'r. DRAKELEY ET AL TRACK-TYPE LANDING GEAR 3 Sheets-Sheet 3 FiledJuly 11, 1949 INVENTOR. GEORGE 7'. DEA/(LEV By DONALD w. FM/LAY ATZ'OENEYS III/II more sensitive than the hard unit to forces of thisnature, the net effect On the hard unit is negligible, and this can beconsidered to be substantially as sensitive to abrupt shocks duringbraking as it is in the absence thereof. In the ultimate result theshock absorber is left free at all times to absorb such ground loads asit was designed to absorb, the transmission of forces to the airframe isminimized at all times, the tendency to pitching is largely eliminated,and the area of ground contact of the track band, and the effectivetractive or braking area, remains generally constant. 7 I

The provision of a combination and arrangement of the parts of atrack-type landing gear to these ends is the primary object of this in-'vention.

More specifically, it is an object to devise a track-1anding gearwherein it is feasible to employ and obtain the benefit of such atandem, hard-soft unit shockabs'orber, so that the same is substantiallyfully operable at all times and under all conditions of'use, andin whichsuch shock absorber neither interferes with braking nor is itselfadversely affected by braking.

The present invention, then; comprises the novel track-type landinggear, which includes in particular the relativearrangement andcoordination of a front braking wheel, a bogie wheel intermediate thebraking wheel and another bogie wheel rearwardly of both, and a shockabsorber-and in a special form, a shock absorber having the generalcharacteristics indicated-operatively connected'to the intermediatewheel, all as shown in the accompanying drawings in a typical form, andthe principles whereof will be hereinafter more fully disclosed andclaimed.

The accompanying drawings illustrate a practicable embodiment of thepresent invention in a track-type landing gearfor aircraft.

grammatic side elevation view of the landing gear, showing whencevarious parts have been removed, omitted, or simplified in form, insolid I lines the taxying. position of the parts (which also is thebraking position, and corresponds to the position of parts in Figure l),in dashlines the relaxed or-airborne position of the parts, and indot-dash lines a shock-loaded position of the parts. i f

Figure 4 is an axial sectional .view of a typical tandem shock absorbingelement, such as is .used in the present landing gear. Figure 5 is adiagram of theforces acting at the time. of brake application.-

The frame which is the backbone of the land ing gear consists in generalof a central structure S which in part may be bifurcated, but whichincludes a forwardly projecting horn 90,

which in efiect is integral with themain frame.

This frame is supported from the aircraft structure in any I suitable"way, as, for instance, through the shock strut 8 pivotedtdthe. frame at98, and by an extensible jack or'cor'npression strut 80 connected to theframe at '99. The" the aircraft structure;

4 shock strut 8 would usually be formed as a resilient shock absorber.By manipulation of the jack ac and by proper mounting and control of theupper ends of the struts 8 and 88, it is possible for the landing gearas a whole to be retracted and extended, or to be oriented tail down orin any other desired attitude with relation to Such details are no partof the present invention, save that, while ground-borne, the landinggear should be maintained in a constant attitude relative to the groundand to the aircraft, by these or other suitable means.

An endless track band I, preferably grooved at its inner surface tointerfit with and to grip frictionally its supporting wheels, passesabout various wheels I, 2, '3, 39, 31 and 32, disposed in an irregularlyquadrangular pattern about the frame 9, 9E, and supported therefromeither directly or through means which permit them to move, relativelyto the frame'and 'complementally to one another, resiliently inaccordance with shock or other loads imposed upon them. Thus,

for instance, the rear wheel 3| is supported upon rock also abouta-somewhat upright axis.

an L-shaped lever arm 33 (which may be in one piece as diagrammaticallyshown in Figure 3), pivotally mounted at 93 to the frame 9 to rock abouta horizontal transverse axis, and it may, if desired, be articulated asshown in Figure l to Its position is determined by the loading of theresilient shock absorber 34 reacting from the frame 9. The bogie wheels3, 36, mounted in the bogie frame 35, are somewhat similarly mounted-andresiliently supported from the frame 9 by means of the shock absorber36, and the wheel 32 serves,

by reason of the adjustment at 92, as the tightframe 9 and to each otherare not in themselves with similar yielding of the braking wheel I andthe front bogie wheel 2, and it is the relationship of the two latterWheels to each other, to the frame, and to the braking arrangement,which constitutes the primary part of this invention.

whereof is indicated by the numeral 4, and which is pivoted at A8 to theframe 9.

The element 42 is slidable as'a plunger through a head 4! which is theforemost and lowermost end of a cylinder-like intermediate element 43,

which in turn, is slidable as a plunger within the outermost anduppermost cylinder 4. The head .42, hearing the wheel or wheels 2,constitutes a shock absorber element of relatively small mass, havingsmall inertia, which, however, is so heavily preloaded, as by airpressure within the space 44, against which fluidin thespace 45 acts by'way of the interposed free-floating plunger 43, that the whole willyield only underhigh presjsure or loading,not necessarily of largevalue, if abruptly applied, such as willbe producedin taxying over largestones, corduroy surface, or

e8 similar ground irregularitiesm The intermediate pression ebyand'duringsbraking, as a result-of elen1erit -43,acting as a plungerwithin thespace forces-thereby engendered.

41 fthe casing or cylinder 4, -however,.in itself The brakinglwheel lisjournaled about anaxis and through its 'conneetionshas large mass and-defined -by the spindle lll whichx-spindle is .jourinertia, butoperatesagainst much lowerair pres-. 5 -na'led -upon an upwardly andnsomewhatrear- -sure in the upper part-of space -4'I, -hence ismuch wardlydirectedaarm 5 Lot a lever which is pivoted less;-highly preloaded, andwill operate under at fill between itsends toethe for-wardend of the llesser loads, provided they areapplied sufficiently frame horn cfieyandthe longer, ;rearwardly .and

gradually to overcome the higher inertia ofthe asomewhatz downwardlydirected. arm. 5210f the ;;'assembly, -as-,'f0r'-instance, overgroundswells,;= -=--same lever:iseapivotally connectedat'54 to. thedips, or long-undulations. It is the fact that-this head 4|. Themasseof,the.lever-5l,52.and of the "head 4| and its plunger-{-43with-associated-parts Whee1: l supplementsthe-mass of the head 4| is-ofrelatively large mass and consequently and pl-ungen43, to. producethelarge inertia rehigher inertia, which causes itto resistdefiecsistingabrupt -'movementof the plunger 43. tion' under abruptlyapplied forces (which lat- :,-.15 U er o a Co i s, that is to say,-Wh etenmay cause deflection of the head 42), but thereeis no br g eaSeWheHtaXying for whichat the same timepermits it to =yield' to antakeoff;theraisilittle movementof head 42 lesser -shocksthan those whichwill cause move- -=and;=wheel ZreIatiVetoEthe-element 43, thestiffmentof the more highly loaded head 42,- promess- 0fthealoweriresilientelement preventing,

-vided: they are-more gradually applied. The con-e butmo-vernentoftheheadAl which accompanies structionand arrangement of ashockabsorber the movement ofvthe soft plungerAewithin its 'to' theseends is shown in Figure 4 of this appli- -cylinder 4 -Will-efiectmovement of. the braking i'cation, and in greater detail in'thecompanion wheel:l somew e pp y 0 flndecompensatapplication-Serial--Nou104-,052, referred to hereinfi ely Wi hr lation totheentrained movement. above. However, sinceany suitable arrangementagsfithetfrontbogie-wheel2, by reason o -Q of shock absorbingmeans to -thesame, end, and metrical arrangement and connection of. the bell. havingsimilar"characteristics,-0r even a singlenk leversfil 52. .At.. the:sametime, S a p, tm i absorbing means, may besubstitheavyz shocksaslwhenlenco-untering aboulder, tilted: therefor, it is not consideredthat any parewlmbe-accommodated y yielding M the d. Tticularconstruction in detail oftheshock abjao -p fi W s cylinder '43,-but With-- we is part of thjs invention, and hence tout,materialiyielding. of the soft unit because of --showing herein isconsidered as illustrative rather '1itshigherineltiaeand thisresult-W111 take p a -t restrictiva without disturbance-.of-xthebrakingwheel I to The-application of a braking force to thebrakeany'ematerialdegmfi ins wheel-inroduces-a dragon the trackbandl xs5e-Beeekeing Creme-Wheel l fq c rcf' and i t upon 1 ground t Which'thelower :ithe-track' 1,-occursabout the:.aX1s..l.0 OI the Wheel.

harizomal portion ay band, between ;..i.- e iny suitable for-rnnf. brakemay. 'be'employed, i'. 2 andsgyiisengaged' such dragtemmm ceandithat1llustrated1s 1ntended as typical. only. "thetrack band between thebraking wheel! and eXammeWand-as shown m Figure 2, the

thebogie wheel 3, and tends tostraightenthe-40-spind1ee49lcarriesisleeves 59, which ay be bandhetweenlthese twoWheels. Thisproduces ...pressed-.on or..o.t herwi-seheldnonrotatively tothe Enforce material amount and duration, spindle, and insimilar-fashion ashort brake remg upwardly upon t from bogie wheeliz,which zaetionarmaiel :Lissecured. to..or integral with the- --if'not otherwiselresisted would push'the wheel" 2 m LThese' 'ielements' 68 5!with the: -upwardly, and would use up most or all its r Sp-1ndleall)constitute in effect a unitary brakelsistancexto compression,- leavingno Cushioning torque reaetionelement, whichis oscillatablysupf'jorlrouljid lgzad sfilpagticulaftrtlyii'tliie soft, less 333:3 ggi f'iigg'gig i i gx if 5 reoade nifi e r o e e 51 ass ownm fii ,gfmmg g'g 23,525 21 9 :=rEigure-.2,. are= journaled by antifriction bearings rnainpivot support 98, and the resultant of Such. e' tsgeeveszfifi and maybe-i y ..eesse aeach. receiveranv expansive. braking ele- 43 e mug theframe 9 pli-ach abmit mentzfieb.earingva..braking shoe 62 which bears Velvot at 98 or to tend so to do, partlcularly if within the pfiripheryof th Caviy Within the thefro nt b gie Wheel 2 isforced upwardly. It 7ae e e highly desirable ee prevent the 5531 2512 ?i 3331?ig fiilttfitniiffiicttfit iftiII umtOf-the Shockabsorber m Q P F -;tion ofthervvheel would by reaction tend to lng2under--SuCh forces yet deslgn1t 15 .--.'effect-'.rotation .of..the brake reaction. a m. in ,herently.yieldable to just such forces if they are i I:,-,the.asamecounterclockwise .sense, as viewed in =e=aPP11d$ufiiC1ent1ygradually throughout a "Eigllre ll-such rotation is resisted byanchoring sumcientperiod of time to overcome the inertia ;the brakereactionimember El to the frame, of ,the; head 4i and p un 431Etssociated'v i i e. movement ofgthei lever 5i, 52,.u'nder non-- parts.I The solution adopted is to cause brake braking conditions must not berestrained, the application to react automatically, and, in this s'a lQl p 'il fin fii .t k sthe form of .the torq particular form, throughmechanical linkage and li at correctly calculated mechanical advantage,to e'Toiund-erstand the effect when braking occurse Ttresist compressivemovement of the soft resilient 651-0911315161 the extreme'ca'se if thebrake Were .yzunitAS, 4 to such degree as is necessary to resististmpgly as lock the Wheel I to the ,uthe-compressive effect of.braking, leaving it free brake "reaqtlonmement which includes thetecompress, as'before, under loads otherwise de- 6 Y H The continuedcountercl k "*P 'a P bfaen descnbf3d as lock 70, on thewheel I can notnowi t tt hg t t ei gtfi t Soft t W m 1S descrlptlve except thesnindlelfl but th Wheel is still free to r l Complete inabilityofthe 0 Ui jtatel bodilvlcountercloc swise about the outer ei d t compre s; it-dr ta tha ability W u ,lottiiarfii Bl, wherethe latter .ispivotallysesubstantialdiminution, and the flocking out? is cured tofthe;torquelink .63. QBy reaction through only the automatic'neutralizationof its com-' the o'scil1atableconnecti0n between the aun6i and the short lever arm 51, this produces a clockwise torque on thelever 52 about its pivot axis at 58, urging generally downwardly thelonger lever arm 52 and the front bogie wheel 2.

Any such locking of the wheel I while the track moment about the mainpivot support 98, and a resultant reaction at the front bogie wheel 2urging the latter upwardly, and tending to straighten out the track bandbetween wheels l and 3.

Thus there are at least two forces acting on the front bogie wheel 2,the one urging it downwardly, the other urging it upwardly. If by designthese opposed forces are made generally equal in value as well asopposite in sense, it follows that the soft shock unit is not compressedeven by the locking of the braking wheel I, and the forces therebyengendered. Briefly, the brake torque reaction may be considered asapplied to the soft unit to counteract the force acting thereon as aresult of brake torque; this condition prevails throughout braking, andgenerally speaking the counteracting force automaticaily equals thedistorting force at all stages and values. The braking which caused thetendency 'to push upwardly the head 4!, automatically has produced anequivalent resisting iorce, holding it against upward movement.

Braking will not ordinarily lock the wheel I, but in all cases, and towhatever extent the brake is applied, the resultant reaction between thelink-held brake reaction arm 6i and the lever arm 51 tends to resistforward movement of lever arm 5! and upward movement of arm 52, to thatextent-that is, in consonance with .the applied braking forceresistingcompression vof the soft resilient element 43, 4.

The result of brake application may be understood in detail by referenceto Figure 5. The application of braking force at '52 between therotating wheel I and the non-rotative spindle 68 transmits a couple F5through brake reaction arm 18E to torque link 63 and the short upper arm5| :of the crank lever Si, 52.

This tends to rotate that crank lever in a clockwise sense about its.fixed fulcrum at so, so that it places a downward load F3 on the head iof the tandem shock ab- This downward force F3 is used to neutralize anincreased upward force F2 made up ;primarily by the forward shifting ofthe center .of contact pressure of the track band 1 under the influenceof the couple Fl, and to a lesser degree by the increase in upward loadon the bottom of the tandem shock absorber as a result of increased belttension caused by braking action of wheel I on the track band 1. Thus itis seen that brake application immediately and automatically effects adownward load on the head 4! and an upward load at the lower head 42,thus further compressing the lower hard shock absorber unit but does notmaterially affect the upper soft shock absorber unit. Proportions ofcrank arms of linkages, of the brake forces, and of the shock absorberresistances, can be so chosen as to obtain a downward load on the head Mwhich is sufficient to neutralize the added upward load on the lower end42 of the shock absorber caused by braking, but not materially in excessof a neutralizing force. Since braking loads on the shock. absorber 4,4|, are

shock absorber can continue to operate during braking in substantiallythe same manner as in the absence of braking. The hard shock absorber42, 4! is affected more or less by braking loads, the degree thereofdepending on the abruptness of application of such loads, and the designof the particular unit employed. Being designed, as already explained,in such manner that it responds primarily to abruptly applied loads, butnot so readily to more gently applied loads, even of large va-ue (sinceany such gently applied load is at any given instant small in comparisonto its own high preloading), this hard shock absorber is not ordinarilygreatly affected by the relatively gradual forces set up during braking,hence it too retains to a material degree its ability to yield to abruptshocks which may arise during braking.

Notwithstanding the looking out of the soft unit, 43 within 4, duringbraking, the ability of that unit to respond to and absorbground-induced loads is substantially as great as it possesses in theabsence of braking. If a ground load is imposed on it during braking,such load is superimposed on the load arising from braking; since onlythe brake-induced load is neutralized, the excess or superimposed groundload produces normal deflection, just as it would in the absence ofbraking. Nor does such lookin out affect the ability of the hard unit,42 within 43, to deflect under abrupt loads. The resistive force isapplied to the head 4 1, hence does not in any wise apply to nor affectthe movable element 42 of the hard unit. This remains free at all timesto yield to abrupt loads.

We claim as our invention:

1. In a track type landing gear, an endless track band, a frame; a frontbogie wheel, a braking wheel ahead thereof and upraised thereabove, andadditional wheels, all wheels being supported from said frame andarranged in a pattern to receive and guide said track band and. tomaintain a material length of the same, from the front bogie wheelrearwardly, in ground contact while the landing gear is ground-borne; amain pivot support for the frame, located above ground level and behindthe braking wheel and the front bogie wheel, about which the landinggear tends to pitch upon brake application; resiliently yieldable meansmounted on said frame, forwardly of said main pivot support, andoperatively connected to said front bogie wheel to resist its upwardmovement towards the frame under the influence of surface irregularitiesand of braking-induced pitching; means separate from but mounted on andfor movement relative to the frame, operatively connecting said frontbogie wheel and said braking wheel, through said yieldable means, tojournal the braking wheel and to displace the same bodily and generallyoppositely to movement of the front bogie wheel, to maintain the trackband taut; brake means reacting, upon brake application, from said frameupon the braking wheel to resist its rotation, and by reaction upon andthrough said separate means connecting the front bogie wheel and thebraking wheel tending to displace the braking wheel and the front bogiewheel in the sense toneutralize braking-induced upward movement of thefront bogie wheel, and consequent upward deflection of the yieldablemeans under the influence of braking forces alone.

2. A track-type landing gear as in claim 1, including additionally asecond resiliently yieldable n c eeatmeans.:of:.=.yieldabilityicharacteristically differing from that ofthe-first resiliently yieldable means,

interposed between :the latter and 'the'sepa'rate means connecting thefrontlbogie wheel and the braking wheel, on the one 'hand, and the frontbogie wheeL: on the other hand, to afford yieldability of the frontbogie wheel and of the track hand independent y of the 'y'ieldabilitycharacteristic of the first such means.

3. A track-type landing gear as in claim 1, wherein the resilientlyyieldable means includes a shock absorber unit mounted upon the frameand including a plunger element mounting the front bogie wheel to urgethe latter downwardly, and wherein the separate connecting meanscomprises a lever pivotally mounted between its ends upon the frame, itsone end being operatively connected to said plunger element to rise andfall therewith, and its other end mounting the braking wheel and thebrake means.

4. A track-type landing gear as in claim 3, wherein the braking meansincludes a brake reaction arm, brake resistance means reacting betweenthe braking wheel and said brake reaction arm, and a torque linkpivotally connecting the outer end of said brake reaction arm to theframe, and constituting a fulcrum for pivotal movement of said brakingwheel and the lever arm whereon the same is mounted, upon brakeapplication tending to lock the brake reaction arm to the braking wheel.

5. In a track-type landing gear, an endless track band, a frame, a frontbogie wheel, a braking wheel ahead thereof and unraised thereabove, andadditional wheels, all wheels being supported from said frame andarranged in a pattern to receive and guide said track band and tomaintain a material length thereof, from the front bogie wheelrearwardly, in ground contact while the landing gear is ground-borne; ashock absorber unit including a cy inder mounted upon the frame and adownwardly-directed plunger reciprocable therein: the front bogie wheelbeing mounted upon said plunger, a lever pivotally mounted between itsends upon said frame, having a rearwardy directed arm conn cted to saidplunger and an upwardly directed arm whereon said braking wheel isjournaled, brake reaction means, inc uding a brake reaction arm, alsomounted upon said upwardly directed lever arm, brake torque resistingmeans interconnecting said brake r action arm and the frame, and brakemeans reacting bet een the brake reaction means and the braking wheel.

6. In a track-type landing gear, an endless track band, a frame, a frontbogie wheel, a braking wheel ahead thereof and upraised thereabove, andadditional whees, all wheels being supported from said frame andarranged in a pattern to receive and guide said track band and tomaintain a material length thereof, from the front bogie wheelrearwardly, in ground contact while the 'landing gear is ground-borne; atandem shock absorber unit including a cylinder mounted upon the frameand a first downwardly-directed plun er reciprocable therein under theinfluence of relatively soft forces, and a downwardly-directed secondplunger reciprocable in the first plunger as its cylin er under theinfluence of relatively stiff forces; the front bogie wheel beingmounted upon said second plunger, a lever znaleid, brake 'frea-ction'means, incluclingsav brake zreactionxarmgalso :mounted uponsaidiupwardly directed-lever arm,.rbrake,torquerresisting. means:interconnectingsaidtbrake'reactionrarmrand the .framagand brake "meansreacting between the brake? reaction meanszandz the :brakingwheel;

flrAatracketype landinge gear comprising an L'eIl fileSSlEtla'CkIbBMiJfil frame ;:a front bogiewheel, .a'ibrakingr. wheel.=.ahead= thereof and elevated thereabove;arearxzwheel,zadditional=bogie wheels intermediate the front bogie wheel and thezrear wheel, anupper wheel supported from the frame, resiliently yieldable meanssupporting all wheels except the upper wheel from the frame and arrangedin a pattern, including the upper wheel, to receive and guide said trackband and to maintain it, between the front bogie wheel and the rearwheel, in ground contact while the landing gear is ground-borne; asupport carried by and for movement relative to the frame, andconstituting the immediate sup ort of said braking wheel, said supportbeing operatively connected for movement with the front bogie wheel,relative to the frame; brake reaction means carried by said support andanchored to said frame; and brake means reacting between said brakereaction means and said braking wheel.

8. A track-type landing gear including a frame, an endless track band, aplurality of wheels including a front braking Wheel and an adjacentfront bogie wheel, disposed about said frame at stations to receive andguide said track band, and means supporting the several wheels from theframe for generaly complemental resilient yielding movement to maintainsaid track band taut under the influence of ground forces or shock, andreaction therefrom; wherein the supporting means for said front bogiewheel comprises a tandem shock absorber including a head re ative towhich the front bogie wheel is resiliently yieldable under the influenceof large abrupt loads, and which is itself resiliently yieldablerelative to the frame under the influence of gentle, less abrupt loads,and wherein the supporting means for the braking wheel comprises a leverpivoted between its ends upon the frame and having a short, upwardlydirected arm whereon the braking wheel is journaled for rotation aboutsaid wheels axis and a long, rearwardly directed arm operativelyconnected to said shock absorber head; a brake reaction member carriedupon said lever and oscillatable about the axis of the braking wheel,brake means reacting between said reaction member and said brakingwheel, and a torque link connected to the frame and restraining suchoscillation of the reaction member.

9. In a track-type landing gear, an endless track band, a frame, aplurality of wheels, including a front bogie wheel, distributed aboutand supported from said frame in a pattern to receive and guide saidtrack band and to maintain a material length of the same, from the frontbogie wheel rearwardly, in ground contact while the landing gear isground-borne, one of said wheels constituting a braking Wheel, brakingmeans operatively associated with said braking Wheel, mounting means forsaid braking wheel, carried by and movable relative to the frame, formovement of the braking wheel automatically in response to forcesproduced by brake application, and organized and arranged that by suchmovement a force is produced, so directed as to tend to move upwardlythe front bogie wheel, resiliently yieldable means reacting between theframe and 2,544,985 12 v said front bogie wheel to resist the latters10. A track-type landing bear as in claim 9, upward movement, andbrake-reaction means including supplemental resiliently yieldableautomatically operable under the influence of means interposed directlybetween the first such brake application, reacting between the framemeans and the front bogie wheel.

and said mounting means for the braking wheel, 5 GEORGE T. DRAKELEY. tocounteract such movement of said mounting DONALD W. FINLAY. means to thedegree that brake application tends to efiect such movement, and therebyrelieving N0 r f r n s i e said resiliently yieldable means fromcompressive forces acting thereon as a. result of brake application.

